Calibration Of Measuring Devices Research Articles

Modelling methods for pressure balance calibration

Calibration of pressure balances at the highest metrological level consists of determining the effective areas Ap of the piston-cylinder assembly as a function of the pressure. The values of these effective areas are then analyzed to determine the effective area at null pressure A0 and, if significant, the distortion coefficient λ. However, several approaches used to determine these parameters and associated uncertainties can yield significantly different results. With a long experience in the calibration of measurement devices, LNE has developed a software package LNE-RegPoly which estimates the calibration function with weighted regression methods.This article describes the different models commonly used to determine Ap and λ, outlines a method to overcome the covariance calculations, then shows the results obtained with the software when processing the calibration data taken from a Euramet project.

Standardization of physical measurements in European health examination surveys-experiences from the site visits.

Health examination surveys (HESs) provide valuable data on health and its determinants at the population level. Comparison of HES results within and between countries and over time requires measurements which are free of bias due to differences in or adherence to measurement procedures and/or measurement devices. In the European HES (EHES) Pilot Project, 12 countries conducted a pilot HES in 2010-11 using standardized measurement protocols and centralized training. External evaluation visits (site visits) were performed by the EHES Reference Centre staff to evaluate the success of standardization and quality of data collection. In general, standardized EHES protocols were followed adequately in all the pilot surveys. Small deviations were observed in the posture of participants during the blood pressure and height measurement; in the use of a tourniquet when drawing blood samples; and in the calibration of measurement devices. Occasionally, problems with disturbing noise from outside or people coming into the room during the measurements were observed. In countries with an ongoing national HES or a long tradition of conducting national HESs at regular intervals, it was more difficult to modify national protocols to fulfil EHES requirements. The EHES protocols to standardize HES measurements and procedures for collection of blood samples are feasible in cross-country settings. The prerequisite for successful standardization is adequate training. External and internal evaluation activities during the survey fieldwork are also needed to monitor compliance to standards.

Fuzzy multi-objective decision model for calibration supplier selection problem

Quality products and competitively priced services are crucial in today’s global markets. To provide quality at an acceptable price, companies seek out not only raw material and product suppliers but also calibration services suppliers. The calibration of measurement devices is one of the ISO9001 standard requirements for quality. Although companies select and manage their calibration processes as economically as possible, cost is not their only selection criterion. Technical capability, documentation competence, performance history, warranties, and communications are also considered when selecting calibration suppliers. There are numerous criteria and methods in the current literature on supplier selection, but few studies have specifically examined the selection of calibration suppliers.This paper is the first study that specifically examines the selection process for calibration suppliers by utilizing selection criteria that were researched and presented prior to this study. Due to the varied linguistic expressions of criteria and the uncertain model parameters, this paper presents a fuzzy approach for selecting a calibration supplier. The model contains relevant calibration service quality parameters such as the weight of criteria, cost, calibration time, demand, technical capability, and number of experts. This study proposes a fuzzy multi-objective linear programming model that assigns the calibration supplier to the measurement device using two objectives: maximizing the fuzzy weight of the criteria and minimizing the fuzzy calibration cost through fuzzy calibration time, the number of certified experts, the technical capability of the company, and the measurement device demand. A two-phase approach is used to solve the fuzzy multi-objective decision model. Weight, cost, and calibration time are handled as fuzzy numbers for modelling the imprecise data. In an actual application, calibration suppliers are selected for 20 measurement device types and 161 measurement devices with the fuzzy multi-objective linear programming model.

Fast principal component analysis of large data sets based on information extraction

AbstractPrincipal component analysis (PCA) and principal component regression (PCR) are routinely used for calibration of measurement devices and for data evaluation. However, their use is hindered in some applications, e.g. hyperspectral imaging, by excessive data sets that imply unacceptable calculation time. This paper discusses a fast PCA achieved by a combination of data compression based on a wavelet transformation and a spectrum selection method prior to the PCA itself. The spectrum selection step can also be applied without previous data compression. The calculation speed increase is investigated based on original and compressed data sets, both simulated and measured. Two different data sets are used for assessment of the new approach. One set contains 65 536 synthetically generated spectra at four different noise levels with 256 measurement points each. Compared with the conventional PCA approach, these examples can be accelerated 20 times. Evaluation errors of the fast method were calculated and found to be comparable with those of the conventional approach. Four experimental spectra sets of similar size are also investigated. The novel method outperforms PCA in speed by factors of up to 12, depending on the data set. The principal components obtained by the novel algorithm show the same ability to model the measured spectra as the conventional time‐consuming method. The acceleration factors also depend on the possible compression; in particular, if only a small compression is feasible, the acceleration lies purely with the novel spectrum selection step proposed in this paper. Copyright © 2002 John Wiley & Sons, Ltd.